Pressure reducing valve



Feb. 27, 1962 J. J. PIPPENGER PRESSURE REDUCING VALVE 2 Sheets-Sheet 1 Filed Sept. 22, 1958 Feb. 27, 1962 .1. J. PIPPENGER 3,022,794

PRESSURE REDUCING VALVE Filed Sept. 22, 1958 2 Sheets--Shee'cl 2 nited states @arent 3,622,794 PRESURE REDUCING VALVE John I. Pippenger, Manchester, Mich., assigner to Double A Products Company, Manchester, Mich., a corporation of Michigan Filed Sent. 22, 1958, Ser. No. 762,534` 6 Ciaims. (Cl. IS7-H63) This invention relates to pressure reducing valves and particularly to a pressure reducing valve that can be subjected to relatively high inlet pressures without leaking.

The maximum iiuid pressure at which conventional pressure reducing valves can be operated is limited by the leakage within the valve due to manufacturing tolerances and the like. Consequently, most pressure relief valves are limited to maximum inlet pressures in the neighborhood of approximately 1500 p.s.i. and require special drain lines to carry off the leakage within the valve.

In applications, such as for use in submarines, leakage within the valves cannot be tolerated since the valve is generally connected to an accumulator and such leakage would require the submarine pumping units to operate more frequently to maintain the charge of the accumulator at the desired pressure. Since there are long periods under combat conditions when submarines are being hunted by ships using sound detecting equipment, it is obvious that the pumping units cannot be operated to charge the accumulators during such periods. Yet the accumulators must retain their charge in order to be able to provide immediate pressures at predetermined magnitudes at all times. Therefore, a non-leaking pressure reducing valve is required for submarine applications to prevent the accumulator charge from being dissipated through leakage and thus obviate the need for operating the pumping units when the submarine is subject to detection by enemy ships.

In other applications, such as in oil well digging operations, relatively large fluctuations in the volume of pressurized fluid required are encountered. The simplest and most economical Way to meet such large volume demands with accumulators is to charge the accumulator to a higher pressure so that it will hold a greater volume of iluid. However, as previously stated, conventional pressure reducing valves cannot withstand pressures in excess of approximately 1500 p.s.i. and, therefore, rather than charging one accumulator to a higher pressure additional accumulators charged to a maximum of 1500 p.s.i. must be provided to provide the required uid volume when employing conventional reducing valves. This, of course, multiplies the number of valves and other equipment needed in addition to multiplying the number of accumulators needed.

Consequently, in such an application, it would be very desirable to have a pressure reducing valve that could be subjected to higher inlet pressures of approximately 3000 p.s.i., for example, so that the charging pressure of each accumulator could be increased to reduce the number of accumulatore required.

Therefore, it is one object of the invention to provide a pressure reducing' valve that can be subjected to relatively high inlet pressures without leaking.

It is another object of the invention to provide a pressure reducing valve which is analogous to a two-way valve in that it permits pressurized fluid to freely'pass therethrough when the outlet pressure is relatively low and which progressively seals olf the high pressure inlet port as the outlet pressure increases, the inlet port being cornpletely sealed ofi when the outlet pressure reaches a predetermined value.

It is a further object of the invention to provide a pressure reducing valve having a built-in pressure relief valve for preventing the outlet pressure from exceeding a predetermined value.

It is a still further object of the invention to provide a pressure reducing valve having means thereon for selectively controlling the maximum outlet pressure that can be obtained, and having a built-in pressure relief valve which automatically functions at pressures proportional to the maximum outlet pressure of the reducing valve to prevent the outlet pressure from exceeding the maximum pressure selected.

It is a still further object of the invention to provide a pressure reducing valvewherein the outlet pressure can be varied over a wide range and wherein the variation of the maximum outlet pressure can be remotely controlled.

Other objects, features and advantages vof the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIGURE l is a sectional view of a pressure reducing valve embodying features of the present invention;

FIG. 2 is a sectional view takenalong the line 2-2 of FIG. l;

FIG. 3 is a sectional view taken along the line 3-3 of FIG. 2;

FIG. 4 is a sectional view taken along the line 4 4 of FlG. 2;

FIG. 5 is a sectional view taken along the line 5 5 of FIG. 2;

FIG. 6 is an enlarged fragmentary sectional view of the seal seats taken along the line 6-6 of FIG. 5,; and

FIG. 7 is a broken sectional View of a modication of the valve illustrated in FIG. 2.

Referring to FIGS. l and 2, a valve embodying features or" the present invention is comprised of a valve body 10 having an enlarged chamber 12 therein. A cover plate 13 is fastened thereto by suitable bolts i4 or the like and a bottom plate i6 is fastened to the other end of the body by suitable bolts 17 to enclose the chamber 12 within the body. A subplate 1S (illustrated in dotted and dash lines) may be bolted to the bottom plate 16 by suitable elongated bol-ts 20 or the like extending through the cover plate 13, body 16 and bottom plate i6 for a purpose which will be described in greater detail hereinafter.

A disc-shaped ported plate 22 h-aving a depending hub portion 24 is rotatably mounted within the chamber 12 by a bushing 26. It will be observed that the hub portion 24 is rotatably positioned within the bore of the bushing 26 by needle bearings 2S and that suitable roller bearings 30 are disposed between the end of the bushing 26 and the adjacent face of the ported plate 22 to eliminate the friction therebetween when the ported plate is forced against the end of the bushing 26 by fluid pressure vwithin the chamber 12, as will be described in greater detail hereinafter. Washer-shaped bearing plates 3i are provided on either side of the roller bearings 30 to reduce wear on the ported plate 22 and the end of the collar 26. A retaining ring 32 is disposed about the roller bearings 30 and a spring 34 is disposed between the retaining ring 32 and an annular flange 36 on the left end ot' the collar 26, as viewed in FIG. 2, to urge the ported plate 22 and collar 26 in opposite directions.

An O-ring 3S is positioned within an annular groove in the annular ange 36 for slidably bearing against the wall of the chamber 12 to prevent pressurized iiuid from leaking therepast and a disc d@ having an O-ring 42 disf posed thereab-out is positioned within the bore of the collar 26 to prevent pressurized uid from escaping therepast. In this manner, the O-rings 3S and i2 prevent pressurized fluid from escaping out of the chamber 12 by passing between the cover plate 13 and the body 10.

As most clearly illustrated in FIG. 1, which is a section through the ported plate 22, the ported plate has a port le opening on the right face thereof, as vviewed in FIG. 2, which communicates with generally radially outwardly extending ports 46 which in turn communicate with the chamber 12. A notch de and a slot SG are cut into the periphery of the ported plate 22 with 'the slot extending from one side of the notch between the faces of the ported plate. A link member 52 'has one end thereof pivotally connected within the slot Sti by a pin l541 and the other end thereof pivotally connected within a slot 56 on the end of a piston 53 by a pin 60. With this construction, the ported plate 22 can be rotated through a limited angle by the reciprocation of the piston 58, as will be described in greater `detail hereinafter.

A ported disc 62 is positioned on the right face of the ported plate 22, as viewed in FIG. 2, by a vdowel pin 6e or the like, and is bolted thereto bya bolt 66 or the like. As most clearly illustrated in FIG. 3, the ported disc 62 has three relatively small triangularly spaced ports 68 extending therethrough, each of which -is aligned with the port 44 of the ported plate 22.

As most clearly illustrated in FIGS. 2 and 6, a seal seat assembly '70 is disposed between the ported disc 62 and the bottom plate 16 and is briefly comprised vof aretaining ring 72 fixed to the bottom plate 16 having two spaced holes 74 and 76 therein. Two telescopi-ng sleeve assemblies 73 and 80 are positioned within each of said holes, respectively, with one end bearing against the bot` tom plate 16 and the other end bearing against the ported disc 6-2.

Each of the telescopng sleeve assemblies comprises an outer sleeve 82 having an O-ring S4 disposed within an annular groove on the end thereof bearing against the bottom plate 16 to provide a seal therebetween, and a sleeve 86 slidably disposed within the sleeve 82. An 0- ring 58 is disposed between each pair of sleeves to provide a sliding seal therebetween and a spring 90 is also disposed between internal shoulders oneach pair of sleeves to urge them apart so that the ends thereof bear against the faces of the bottom plate 16 and ported disc 62. Telescoping sleeve assemblies of this type are completely described and claimed in a copending kapplication of James W. F. Holl, Serial No. 352,675, tiled on May 4, 1953, now Patent No. 2,832,561 and assigned to the assignee of the present invention and reference is made to the copending application for a more detailed description of such telescoping sleeve assemblies.

It will be observed that the diferential areas of the telescoping sleeve assemblies which are exposed to lhuid pressure either inside or outside thereof are such as to bias each of the sleeves against their respective faceswith a force in addition to that provided by the springs v90 for urging the sleeves against their respective faces. It will further be observed that the sleeve S6 ofthe telescoping sleeve assembly 86 has an` annular shoulder 92 formed on the outer surface thereof so that `it is urged against the face of the ported disc`62 when e'rrposedlto pressurized fluid within the chamber 12 only as will be described in greater detail hereinafter.

The bottom plate 16 has three ports 'extendngtlierethrough, an inlet port 94 aligned with the telescoping sleeve assembly "7S, an outlet port 96 which is notaligned with either of the telescoping sleeve assemblies but' does communicate with the chamber 12, and a pressure relief port 9S which is aligned with the-telescoping sleeve assembly Si). These ports are most clearly illustrated in FIGS. 4 and 5, and it will be observed that the fa'ce of the bottom plate 16 illustratedin FIG. 4` has an annular groove 161i thereinabout the ports 94, 96and 98 for receiving an O-ring 162, as illustrated in FIG.2, to provide a seal between the bottom plate and body 10, and that the face of the bottom plate illustrated in FIG. is provided with four annular grooves 104, 105, 108 and about each of the ports 94, 9S, 96, anda drain port 112, respectively. The drain port-112 extends through the l'botdtom plate 16 for a purpose which will be described in gr'er detail llriilf.

Suitable O-rings 115 are disposed within each of the annular grooves 1114- to provide a fluid-tight seal around each of these ports between the abutting faces of the subplate l1S and bottom plate 16. With this construction, the subplate 18 can have suitable conduits connected thereto with suitable ports extending therethrough and communicating with the ports extending through the bottom plate 16 to direct fluid runder pressure into and out of the chamber 12. Such a subplate is conventional and, therefore, it is not believed to be necessary to describe it in greater detail.

In operation, the ported disc 62 is normally positioned by the piston 5S and link 52 so that the three ports 63 are completely aligned with the sleeve 86 of the telescoping sleeve assembly 73. Consequently, when the valve is connected in a suitable hydraulic system, fluid under pressure will pass through the subplate 1S, into inlet port 94;- in the bottom plate 16, through the telesco'p'ing sleeve assembly 7S, ports 68, port d-fi and ports 4.6, into the chamber 12 in the valve body 10, and thence from the chamber through the outlet port 96 and the subplate 1S to a device to be operated by the pressurized fluid, such as a hydraulic cylinder or the like.

As the device demands greater fluid pressure for its operation, the fluid pressure within the chamb'er 12 invcreases and acts upon the exposed face of the piston SS to force it outwardly of the body 1li, suitable resilient means 114 being provided for resisting the outward movement of the piston 58, as will be described in greater detail hereinafter. It will be observed that an Oring 116 is disposed within an annular groove about the piston 58 so as to slidably bear within the bore of a collar 118 disposed in a bore 13S in the wall of the body to prevent the pressurized fluid from escaping from the chamber 12.

As the piston 53 moves outwardly against the resistance of the resilient means 114 in response to the increasing fluid pressure within the chamber 12, the ported plate 22 is rotated in a clockwise direction, as viewed in FIG. l, by virtue of the connection provided by the pivoted link 52,

Vto gradually' move the ports 68 out of alignment with the sleeve 86 of the telescoping sleeve assembly 7 8. At a predetermined maximum pressure determined by the magnitilde of the resilient means 114, the piston 5S moves the ports 63 completely out of alignment with the sleeve Se, at which time the entire end of the sleeve S6 seats against the face of the ported disc 62 to completely seal off the inlet port 94. y

In this position, of course, the greater the inlet pressure the greater the force with which the ends of the sleeves 86 and 82 of the telescopi-ng sleeve assembly 78 are urged against the faces of the ported disc 62 and bottom plate 1'6 since, as previously explained, the ditferential areas exposed'to the liuid pressure are such as to self-bias the vsleeves against their respective faces.

As the lluid pressure within the chamber 12 decreases inresponse to the demand by the device to be operated by the iiuid pressure, the piston 58 is urged back into the body by the resilient meansy ldkwhich rotates the ported p`l'atev22i'n'al counterclockwise direction as viewed in FIG. 2 to gradually bring the ports 63 into alignment with the telescoping sleeve assembly 78 and inlet port 9d. By providing three ports 63 rather than one larger port, the

unbalancing forceexerted on the sleeve S6 of the sleeve assembly 78 by virtue ofthe fluid pressure acting on the end thereof overlying theports is minimized to reduce the possibility of the seal seat popping under the tluid pressure, that is, cocking or lifting upwardly to break the seat between the end of the sleeve 86 and the face of the ported disc 62. This feature is completely described and claimedv in la copending application of Ronald L. Loup, Serial No. 7755849, rlledv on November 24, 1958, and assigned to the assignee of the present-invention and reference ismade tothisfcopending application for a more detailed explanation of the operation and advantages of the three ports 68 as compared with one port.

With a valve of this construction having the telescoping sleeve assembly 78 acting on the rotating ported disc 62, it is apparent that a superior seat is provided as compared with prior art pressure reducing valves which enables greater inlet pressures to be used without leakage within the body. Therefore, the valve ofthe present invention is pre-eminently suited for use in connection with applications requiring higher inlet pressures wherein the inlet port must be completely sealed off without leakage when the outlet port reaches its predetermined maximum pressure.

When using pressure reducing valves of the prior art type, a separate` pressure relief valve is generally provided somewhere in the hydraulic system between the outlet port and the device to be operated by the pressurized fluid to prevent the possibility of the pressure acting on the device exceeding the predetermined maximum amount desired. Such an increase in outlet pressure can be due to any number of reasons in connection with the operation of the device, and independent of the operation of the valve.

r1`he valve of the present invention eliminates the need of a separate pressure relief valve being employed in the hydraulic system by providing the telescoping sleeve assembly 80 aligned with the pressure relief port `9S in the` bottom plate 16. As the ported disc 62 rotates in a clockf wise direction, as viewed in FIGS. 2 and 3, in response to increasing lluid pressure within the chamber l12, it moves the port 68 out of alignment with the telescoping sleeve assembly 78 as previously described toward the telescopinfy sleeve assembly 8G, the position of the sleeve 36 of the telescoping sleeve assembly 80 being shown in dotted lines in FiG. 3.

When the fluid pressure within the chamber 12V reaches the predetermined maximum outlet pressure desired, the ports 68 move completely out of alignment with the telescoping sleeve assembly 78 and completely seal off the inlet port as previously described. However, should the outlet port pressure increase, the fluid pressure within the chamber 12 will also increase which rotates Vthe ported disc 62 further in a clockwise direction to bring the ports 68 into alignment with the sleeve 86 of the telescoping sleeve assembly S0 and consequently the pressure relief port 9S, the subplate 18 having a port thereinand conduits attached thereto for connecting the relief port directly to the tank.

Thus, by the simple expedient of providing an additional port in the bottom plate V16 and an additional telescoping sleeve assembly, the hydraulic system is protected against excess of pressures being applied to'the device to be operated without the necessity of providing a separate additional pressure relief valve. Further, the maximum pressure provided by the valve of the present invention can be easily varied, as will be described in greater detail hereinafter, by varying the resistance of the resilient' means 114, and it is apparent that the pressure at which the relief port 98 is aligned with the ports 68 will inherently vary in proportion to the maximum pressure at the outlet port. In contrast to this, when a separate pressure relief valve is provided as in prior art systems, and the outlet pressure of the pressure reducing valve is varied, the separate relief valve will, of course, have to be independently varied or changed if its operation is to be correlated with the new outlet pressure.

Of course, as most clearly illustrated in FIG. 7, the pressure relief port 98 and the telescoping sleeve assembly S0 can be eliminated, so that only the telescoping sleeve assembly 78 is provided and aligned with the inlet port 94, as previously described. With this modification, the ported disc 62 would be rotated in response to increasing fluid pressure within the body 10 as previously described to move the port 66 out of alignment with the telescoping sleeve assembly 78 to seal off the inlet port at the predetermined maximum outlet port pressure desired, however, no provision would be provided within the valve itself for relieving pressures in excess of this predetermined amount since the telescoping sleeve assembly and relief port 98 are eliminated.

Referring to FIG. l, the resilient means 114 which together with the piston 5S provides a pressure responsive means for rotating the ported plate 22 can be any suitable design, but in the preferred embodiment illustrated it comprises a cylindrical housing having a radially enlarged hub 132 on the right end thereof which fits over the flange on the left end of the collar 118 and is fastened to the body 10 by bolts 134 or the like. ln this manner, the collar 11S is also secured to the body 1i) and a suitable O-ring 136 is positioned between the hub of the collar and the bore 133 in the body 10 to provide a Huid tight se-al therebetween. An O-ring 141D is also provided between the Harige of the collar 118 and the enlarged hub portion 132 of the cylindrical housing 136 to prevent any fluid that may escape past the O-ring 116 and into the cylindrical housing 130 from escaping from the housing 130.

A disc-shaped head 142 having a pilot portion 144 proiecting from the left face thereof is positioned within the cylindrical housing 136 and urged against the left end of the piston 58 by a pair of coaxially disposed springs 146 and 145, the other ends of the springs bearing against a' piston 151) slidably disposed within the cylindrical housing 13() and carrying an O-ring 152 on the periphery thereof to seal against the wall of the cylindrical housing.

A suitable end cap 154 having an internally threaded bore 156 therethrough is screwed within the end of the cylindrical housing 130 with an 0-ring 158 thereon engaging the end of the cylindrical housing 13@ to further prevent any iiuid from escaping from the housing. A- threaded stud 166 is screwed into the internally threaded bore 156 and has a knob 162 iixed to the left end thereof by a set screw 164 or the like to enable the stud 169 to be advanced against a ball 166 disposed within a suitable recess 168 in the left lface of the piston 156 to vary the resistance of the springs 146 and 148 to the movement of the piston 58 to the left in response to increasing fluid pressure within the chamber 12 of the valve body 1t). A jam nut 176 is positioned on the threaded'stud 16) between the knob 162 and the end cap 154 and has a handle 172 fixed to and projecting therefrom for rotating the jam nut 170. With this construction, the knob 162 can be rotated to obtain the desired compressive force in the springs 146 and 148, and the handle 172 may be rotated vto urge the jamnut 170 against the end cap 154 to lock the stud in the desired position.

In operation, as the Huid pressure within the chamber l12 increases, it acts on the right end of the piston 58 to urge it outwardly of the body 10 to the left as viewed in FIG. l, which movement is resisted by the compressive force of the springs 146 and 148. Consequently, the fluid pressure within the chamber 12 necessary to completely move the ports 68 out of alignment with the sleeve 36 of the telescoping sleeve assembly 7S and the inlet port 94, is determined by and substantially equal to the cornpressive force of the springs 146 and 148 at this point, and this, in effect, determines themaximum outlet port pressure obtainable as previously described. To vary the maximum outlet pressure, the handle 172 is merely actuated to release the jam nut to permit the stud 161B to be moved either to the left or to the right by the rotation of the handle 162. This decreases or increases the resistance supplied by the springs 146 and 148 to the m0vement of the piston 58 which in turn decreases or increases the maximum outlet pressure obtainable.

Referring to FIGS. 4 and 5, as well as FIG. l, the drain port 112 in the bottom plate 16 communicates with a suitable port 174 in the ybody 10, a portion of which is shown iu FG. i, which in turn communicates with an axially extending port 176 in the iiange of the collar 11S. In this manner, kany fluid that may 'leak past the -ring 116 between the piston S 'and the collar HS and into the cylindrical housing 13) can be carriedA oir ythrough the ports 176, 17d and out the drain port 112 which may be connected to the tank by the subplate 13.

vFurther, if desired, advantage may be taken of the drain port M2 to introduce uid under pressure into the cylindrical housing 13b for increasing the resistance of the resilient means 114 to the movement of the piston SS to the left, it being apparent that the area of thel right face of the head 42 exposed to the fluid,` as illustrated in FiG. l, is less than the area of the left face of the head exposed to the fluid so that the head will be self-biased to the right by liuid under pressure introduced into the cylindrical housing E30. In this manner, the pressurized fluid introduced through the drain port 112 can serve as a pilot pressure to permit both the maximum outletpressure of the valve and the pressure at which the pressure relief valve functions `to be remotely controlled,

While it will be apparent that the embodiments of the invention herein disclosed are Well calculated Vto fulfill the objects of the invention, it will ,be appreciated that the invention is susceptible vto modiication, variation and change without departing from the proper scope or fair meaning of the subjoined claims.

What is claimed is: ,l 2, 1. A fluid pressure reducing valve comprising ajbody having a chamber with an inlet port Vand an outlet port and a pressure relief port each communicating with said chamber, port means within said chamber selectively alignable with said inlet port and said pressure relief port, said p ort means when aligned withsaid inlet port permitting duid to freely pass from the inlet port into and through the chamber and out the outletport, said port means when aligned with said pressure relief port permitting iiuid .to freely pass therethrough from said chamber, and pressure responsive means formoving said port means from a position wherein'it is' aligned with said inlet port to a position wherein it is aligned with said pressure relief port in response to increasing uid pressure in said chamber, said port means moving through an intermediate position between said inlet port and pressure relief port wherein it is completely out of alignment with both said inlet port and said pressurelrelief port.

2. The subject matter as claimed in claim l including seal seat means disposed between said inlet port and port means and between said pressure relief` port and port means for completely seating oi said inlet port and pressure relief port when said port means is moved out of alignment therewith by said pressure responsive means. 3. A iluid pressure reducing valve comprising a body having a chamber with an inlet port and an outlet port and a pressure relief vport each communicating with said chamber, disc means rotatably vmounted within said chamber and having apassageway extending therethrough communicating with the opposite faces thereof and alignable with said inlet port and pressure relief port, seal seat means disposed between said inlet port and one -face of said disc means to completely seal off said inlet'port when said passageway is not aligned therewith, seal seat means disposed between said pressure relief port and said one face of said disc means to completely seal off said pressure relief port when said passageway is not aligned therewith, an'drotating means-for rotating said disci'rieans from .a position wherein said passageway yis aligned with said v inlet .port to ,a position wherein said passageway is a'ligne'dwith said pressure relief port in ref ySpouse to increasing duid pressure in said chamber, said passagewaymoving through an intermediateposition be- Ltweenlsaid inlet port andpressiirerelief port wherein it is completely-out :of alignment with said inlet port and pressurerelief port.

4. `,lt-duid pressure reducing valve comprising a body havinga chamberwith an inlet port and an outlet port and .a ,pressure relief port each communicating with said chamber, discs means rotatably mounted within said chamber and having a passageway extendingtherethrough communicating with the opposite faces thereof and alignable with said inlet port and pressure relief portsaid inlet, outlet and pressure reliefports l'conimu'nicatng with awall portion ofA said chamber substantially paralelto andspacedfrom one faceof said disc means, va iii-st telescoping sleeve assembly disposed between Vsaid wall portionand saidone face andaligned with and fixed relative to `said inlet port, `la second telescoipng sleeve assembly disposed between said wall portion and said one face and alignedwith and vfixed relative ,toasaid pressure relief port, means, for Aresiliently urging the opposite ends of each Qfsaid sleeveassemblies Ainto sealing engagement with saidwall portionand said one face, respectively, and rotating means for rotating saiddiscmeans inrespnse torincreasing Viiuid pressure in said chamber froin a posi-V tion lwherein said-passageway is aligned `with said inlet port to Va position wherein sfaid passageway is aligned with said pressure relief port, said passageway moving through an intermediate position between said inlet port and pressure relief `port wherein it is completely out of alignment with both said inlet port and said pressure reliefport. v 5. The subject matter as claimed in claim 4vwh1e'rein said rotating means includes means for yieldably resisting the rotation of said disc means in response to said increasing uid pressure wherebythe vrriaxirriurn fluid pressure at said outlet port is determined by said resisting means. ,A

6. The subject matter as claimed in claim 4 wherein ASaid rotating means comprises apiston ext ing through a wall of said body and sealed for sliding `rjiiovement relative -tlj1er eto, and link means connecting the endv of said piston projecting within saidvbozdy to saiddisc means whereby said piston is forced outwardly of said body vby said increasing duid pressure Vacting Von the inner end thereof so that the youtward movement of the piston rofates said disc meanls from said position whereinsaid passageway is aligned with `said'inletiliort to said position wherein `said passageway is aligned with said vpressure'relief port.

ire'rescetcaea saisine frais patear UNITED sTATns PATENTS 521,315 nnmaa time 12, 1894 1,006,189 Eisenbise 1 oa. 17, 1911 2,166,875 over-beke '-'July 1s, 1939 2,832,561 ,HQ11 Apr. 29, i958 2,879,797 Guarani Mar. 31,1959

FOREIGN-.PATENTS 62,860' 'Germany 11111625', 1392 

